There are two broad categories of techniques for the treatment of patients who have experienced significant renal failure. The traditional therapy has been hemodialysis, where the patient's blood is passed through filters that will remove the waste material from the patient's bloodstream. The second technique is peritoneal dialysis, where solutions are cycled into and out of the peritoneal cavity of the patient and wastes are removed with the spent solution.
Both techniques operate by the principles of diffusion across semipermeable membranes. In the case of peritoneal dialysis, the membrane that is used is the patient's peritoneal membrane. Although not as efficient as hemodialysis, peritoneal dialysis offers several advantages that have enhanced its desirability. For example, automated devices have been developed that allow a patient to undergo a dialysis treatment at night while the patient is asleep. Utilizing these automated devices allows the patient great mobility and freedom of time.
Peritoneal dialysis can be accomplished in several different modes. In Continuous Ambulatory Peritoneal Dialysis ("CAPD"), the infusion of solution into and out of the peritoneal cavity is accomplished while the patient functions normally throughout the day. The obvious disadvantages of CAPD are the cumbersome devices that must be worn by the patient. Examples of CAPD systems can be seen in U.S. Pat. Nos. 4,747,822 of Peabody and 4,620,846 of Goldberg, et al.
Two types of peritoneal dialysis therapies that are particularly suitable for use with automated systems are Intermittent Peritoneal Dialysis (IPD) and Continuous Cycling Peritoneal Dialysis ("CCPD"). In IPD, large amounts of dialysis solution (up to 40 liters) are cycled through the patient's peritoneal cavity over a 4 to 24 hour period. In CCPD, the dialysis treatment is more or less continuous, with dwell times of 3 to 4 hours at night, and then throughout the waking time of the patient a single dose of dialysis solution is retained within the patient. There are certain advantages to each of these two different therapy techniques.
In both IPD and CCPD an automated dialysis apparatus operates in generally the same manner. The dialysis solution and "tubing administration set" or simply "tubing set" is integrated with the valving, heating and control functions associated with the automated apparatus. In many of the systems, premeasured amounts of dialysis solution are either pumped or delivered by gravity flow to a heating station. At the heating station the solution is warmed to body temperature in order to prevent the uncomfortable sensation of introducing room temperature or cooler solution into the peritoneal cavity. The warmed solution is then allowed to enter the patient via a catheter implanted in the patient's peritoneal cavity. After a period of time (the "dwell period"), the solution is drained from the patient into a spent solution container.
In IPD, a large amount of solution is cycled in this manner over a relatively short period of time. Once treatment is completed, the patient is unencumbered for at least a few days. A disadvantage is the large amount of dialysis solution that must be utilized. Bags containing 40 liters of solution can be difficult to lift for a patient in a weakened condition.
In CCPD and CAPD methods, the same efficiency of results is obtained by increasing the dwell time of the dialysis solution within the peritoneal cavity. The total amount of solution required can therefore be significantly reduced. The obvious disadvantage, is that there is no "down time" for the treatment.
One of the significant items of expense in peritoneal dialysis of all types is the tubing set. Tubing sets vary widely depending on the type of peritoneal dialysis with which they are used and the brand of cycling equipment with which they are used, but all of them have a cost that is significant, especially when one considers that they are used between several times a week and several times a day for years. Tubing sets must be sterile, and so they are normally used once and then discarded. Thus, for example, a tubing set that costs only ten dollars becomes a fairly major expenditure for a patient that receives dialysis once a day, if that dialysis continues for years as it very often does.